Oil, gas, chemical and power plant industries are constantly seeking for efficient in-situ detection of fugitive gas leakages. Most of the gases used (like methane propane benzene etc.) in these industries are highly explosive when mixed with air, most of the leaking gases belonging to the category of greenhouse gases and therefore contributing to climate instability and temperature increase. Although the leakage problem may (mistakenly) be considered as insignificant, it is causing profit-losses to industries that do not take care of leakage problems. New regulations introduced in most of the developed countries require constant monitoring of equipment in order to control and reduce to minimum gas leakage. At it is well known, today there are many different products that facilitate detection of volatile organic components (VOC) and other gases. Most of these products belong to a category named ‘sniffers’. Sniffers provide accurate gas concentration readings but suffer from extensive labor related to the inspection process that has to be performed locally in close proximity with pipes valves or any other gas carrying components.
Optical detection systems are also known.
In US 2005/0156111 (Racca et al.) there was disclosed an imager system for imaging of a plume of a fugitive gas, dependent upon an electromagnetic wavelength absorption characteristic of the gas. A bi-spectral selector assembly houses first and second filters in separate first and second optical paths for transmittal of electromagnetic energies emanating from the scene of interest. The first and second filters have adjacent mutually exclusive narrow band pass characteristics only one of which corresponds to the electromagnetic wavelength absorption characteristic of the gas. An imager captures first and second image data having traversed the first and second filters in a frame which is then processed by correlating the image data to provide displayable data including an indication of any plume of the fugitive gas. The data is displayed in real time. In one example a CCD video camera provides picture data which is displayed with the image of the plume of gas pasted thereupon.
In U.S. Pat. No. 5,656,813 (Moore et al.), there was disclosed an apparatus which remotely visualizes and detects toxic, flammable and other gas leaks and enables one to see gas clouds in real-time. A dual band thermal imaging infrared video camera fitted with a special filter images gas clouds. Image processing is utilized to develop and colorize the gas cloud information for display. The gas image is superimposed over a background image provided by a co-located visible light video camera.
DE 19744164 (Gross et al.) disclosed a high-resolution infra red camera whose narrow-band spectral filter is adjusted for transmission of specific absorption lines of the gas to be detected. A halogen lamp actively illuminates the site of investigation, which is backed, by an infra red reflector. The gas distribution is located between the reflector and the camera. The camera is equilibrated with the illuminated reflector, such that parts of the scene which remain constant over time, do not contribute to picture contrast. For further enhancement of sensitivity, a diffuse infra red reflector is employed. This comprises e.g. an anodized aluminum panel. A measuring location is set up and equipped as described, to detect methane leaks from natural gas lines.
U.S. Pat. No. 5,306,913 (Noack et al.) disclosed method and apparatus for remote optical detection of a gas present in an observed volume using a thermal imager or camera including one or more sensitive elements which are sensitive to radiant fluxes in a determined band of wavelengths, two filters interposable on the optical axis of the camera, the filters having similar transmission bands, one of which includes an absorption line characteristic of the looked-for gas, while the other of which is complementary to said absorption line, and signal processing means for taking the difference between the radiated fluxes received from two points at different temperatures in the volume as observed first through one of the filters and then through the other filter, for taking the ratio of said differences, and for deducing therefrom whether the gas is present in the observed volume.
U.S. Pat. No. 4,555,627 (McRea) disclosed a video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.
U.S. Pat. No. 5,523,569 (Hornfeld et al.) disclosed an apparatus for detecting leakages in structural members. The apparatus includes a device for conveying gas through the structural member to be investigated, a camera having a narrow band filter characteristic matched to the spectral absorption of the gas and a device connected to the camera for processing and displaying the recorded image of the structural member to be investigated.
JP56147034 (Hotsuta et al.) disclosed an imaging system aimed at permitting early detection of the leakage of combustible gases over a wide range by installing infrared ray measuring optical paths in an observation area, detecting the changes in infrared ray laser light absorption by gas leakage and making differential processing and the like. The system comprises infrared ray measuring optical paths, consisting of detecting units 2 and reflection mirrors that are provided in an outdoor observation area where LNG storage tanks are installed. The laser beam of the vibration band wavelength of prescribed mode of leaking methane or the like from the semiconductor laser elements of these units reciprocates in the optical paths and is detected with an infrared ray detector, then the changes in the laser beam absorption in accordance with the concentrations of the leaking methane based on spectral analyses are detected by way of lock-in amplifiers and a divider. The detected values are differentially processed in a differential circuit, and an alarm device operates in real time in response to the methane leakage. Hence, leakage of combustible gases such as methane is detected in an early time over a wide range with the relatively simple constitution.
U.S. Pat. No. 4,390,785 (Faulhaber et al.) disclosed detection of infrared radiation-absorbing or emitting gases in the atmosphere, which can be ascertained by means of an infrared imaging-analyzing means which views a given scene and receives infrared radiation therefrom. Analytic and reference beams are produced, the latter having reduced sensitivity to the gas of interest, and are converted to electric signals, which are processed in real time to provide a signal corresponding to their ratio. This ratio signal is further processed to generate an image, which can be displayed and viewed. This technique is particularly suitable for surveying large areas for seepage of methane or other hydrocarbon gases from underground gas and/or oil deposits.
U.S. Pat. No. 5,867,264 (Hinnrichs) disclosed an apparatus for spectral detection of remote objects. The apparatus consists of an input optic which focuses the field of view onto an image receiving surface consisting of an addressable spatial mask. The mask sequentially projects portions of the scene onto a diffractive optical element which focuses onto a photodetector array. The first image receiving surface of mask is partitioned into independently addressable and controllable subsurfaces, or gates, adapted to receive an electronic control signal from a programmable control signal generator. Each gate in the receiving mask directs a portion of the image incident thereon to a diffractive lens in response to a control signal communicated thereto. This gated image is dispersed by the diffractive lens and focused upon the photosensitive surface of a photodetector array. The photodetector array is partitioned into pixels having a number in ratio to the gates in the addressable mask. The signal output of a pixel within the optical path of the dispersed gated light is sampled and stored in a signal processor. A control signal generator sequentially or randomly addresses each gate in the mask causing the gate to direct that portion of the image thereon to the diffractive lens. The output signal from each pixel on the photodetector array corresponding to the addressed gate in the mask is sampled and stored until the entire image is recorded. This process is repeated as the diffractive optic is scanned through the spectral range of interest. The mask provides enhanced spectral and spatial resolution of the scene (see also U.S. Pat. No. 5,479,258, U.S. Pat. No. 6,680,778 both to Hinnrichs et al.).
U.S. Pat. No. 7,022,993 (Williams et al.) disclosed a leak detector using infrared for identifying the presence and concentration of a selected gas. For detection, radiation from an infrared emitter penetrates the sample, which is analyzed spectrally, and results in a wave length-specific signal being generated at the output. By controlling the optical filter, the radiation is controlled at a selected wavelength, to ensure coverage of all selected compounds. For refrigerants, the selected wavelength can be between approximately 8 to approximately 10 microns. This wavelength obscures other signals, thus minimizing false alarms. The leak detector has a faster time with no adverse impacts on the accuracy of the compound being detected. To further minimize false alarms and to ensure that the emitter does not come in contact with the gas, an additional filter can be used. For refrigerant compounds, the filter can block out signals below approximately 6 microns. For detecting refrigerants, two filters can be used (see also U.S. Pat. No. 6,791,088).
U.S. Pat. No. 6,803,577 (Edner et al.) disclosed a method for quantitative imaging of gas emissions utilizing optical techniques combining gas correlation techniques with thermal background radiation or as self-emission radiation. A simultaneous recording of images with and without filtering through a gas-filled cell is utilized for the identification of a selected gas. A calibration method provides the display of the integrated gas concentration spatially resolved in the generated final image. The procedure includes methods for a correct subtraction of the zero level, consisting of self-radiation from the dual-image camera device including the as correlation cell, and electronic offset, and for the calculation of the specific absorption as a function of the difference temperature between the background and the gas emission.
Other imaging systems which can also be used to detect gases are described in U.S. Pat. No. 5,461,477 (Marinelli et al.).
It is a purpose of the present invention to provide a novel automatic optical gas leakage detection device and method.